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Bruising: a possible side effect of giving blood

Although we hope that no donor will have any ill effects from giving blood, occasionally bruising of the arm may develop. The bruise can look very dramatic and some people may find this worrying, especially if it is not visible until the next day. Bruising can look very nasty, but it is usually harmless and will disperse with time.

What is bruising?

Bruising is caused by bleeding under the skin. The blood usually collects in the area as a bruise although gravity may cause the bruise to appear away from the donation site. With time the familiar blue-black discolouration changes to green, then yellow and eventually fades and disappears. This may take up to three weeks or more if the bruise is large and swollen.

Why can it happen with blood donation?

When the needle is taken out of the arm bleeding will continue until the small hole in the vein closes up. The way to prevent this is to apply pressure to the arm, over the site where the needle was inserted, until all signs of bleeding have stopped. Failure to maintain this pressure is the most common cause of bruising.

Secondly, when the donation needle is put into the arm, damage to the opposite wall of the vein may occur, causing a small hole through which blood can escape. This is not always seen during the donation but may become apparent afterwards.

Thirdly, there are tiny fragile blood vessels running just under the skin, as well as the larger veins from which the donation is taken. When the needle is inserted into the arm, one of these small vessels may be damaged and bleeding occurs. It is impossible to predict this, as such vessels are not usually visible.

Finally, you may also be more likely to develop a bruise if your donation is more difficult than usual or if your veins are difficult to locate or very rarely if the needle damages an artery.

What can be done?

The single most important way of preventing a bruise is to apply pressure to the place where the needle was, until the bleeding has stopped. A dressing will then be applied to the area to keep it clean. It should be kept on for a minimum of 2 hours.

Additionally, if a bruise develops during the donation, we may stop the donation to prevent the bruise worsening. We may also apply pressure on the needle site with a bandage.

What can you do?

Bruising may be painful and you should avoid heavy lifting as this could aggravate the pain. However, gentle movement may be beneficial, as bruising tends to stiffen the arm. Applying something cool to the area can help to relieve any pain or discomfort. A cold cloth or flannel is ideal. If you require more pain relief, we recommend taking Paracetamol (according to the manufacturer’s instructions). However, if you experience any of the following, you should seek further help:

  • Severe pain
  • Pain that radiates up to upper arm / shoulder or down to hand / fingers
  • Numbness or pins and needles in the arm, hand or fingers
  • Swelling and/or redness of the arm

If any of these occur or you are worried you can obtain advice by ringing the WBS on 0800 252266 and asking to speak to a nurse.

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